The present invention relates to a flow control damper and, more particularly, a flow control damper that includes converging portions movable relative to one another to control flow through a conduit such as an HVAC duct.
Various types of dampers heretofore have been used to regulate the rate of air flow through a heating, ventilating and air conditioning (HVAC) duct. Although these prior art dampers have generally performed in a satisfactory manner, some still suffer from various problems. For example, some dampers generate an undesirable amount of noise when in a throttle position or suffer from flutter and instability at their set point adjustment. Some single and multiple blade dampers are difficult to consistently lock at a fixed set point.
Some known dampers may adversely affect the efficiency and/or performance of an HVAC system not only because of their particular structure but also because of the manner in which they are installed. For example, some multiple blade dampers require a complicated support structure that fits inside a duct and interferes with the flow of air through the duct, thereby reducing the volumetric flow rate and/or interfering with the optimal flow path through the duct. Also, some dampers used as power roof ventilator (PRV) backdraft dampers in conjunction with a fan have been known to interrupt the flow pattern into the PRV and thereby deleteriously affect the performance of the fan.
When dampers are installed at the outlets of a duct near diffusers and/or grilles, the flow pattern through the diffusers and/or grilles is disrupted. In some applications, it is necessary to install at least two dampers in series, one in line in the duct remote from an outlet or inlet, and the other at an outlet and/or inlet of the duct. The requirement for two dampers is economically undesirable and creates an inconvenience to install.
When dampers are installed in ceilings, an access door or removal of one or more ceiling tiles may be required to give access to the damper for adjustment. Access doors create additional expense and may be obtrusive. Removing and replacing ceiling tiles is inconvenient and may result in damage to a ceiling tile, resulting in a less attractive ceiling.
The inventor of the present invention appreciated the need for a damper overcoming one or more of the aforesaid drawbacks associated with prior art dampers; for example, a damper that would generate less noise in a position near the outlet or inlet of a duct or more remote from the desired destination of air flow, would not flutter or deviate from its set point adjustment, would improve the flow pattern, would provide regulation of a high percentage of the transverse cross sectional area of a duct, would be adjustable from a terminal outlet or inlet to avoid the need for ceiling space access; and/or would replace the need for both an in-line damper and an inlet/outlet damper.
According to a general aspect of the invention, a damper includes a pair of damper members movable with respect to each other. Each damper member has at least one wall correspondingly inclined to an axis of the damper and the inclined walls are relatively movable between open and closed positions. The walls include plural apertures separated by imperforate portions, and the apertures in each wall are disposed such that the apertures of the inclined wall of one of the damper members are at least partially blocked by the imperforate portions of the inclined wall of the other damper member when the inclined walls are in the closed position.
In an embodiment of the invention, the damper members have a funnel shape. The funnel shape damper members may be sized so that one of the funnel shape damper members may be disposed substantially inwardly of the other funnel shape damper member. To facilitate the relative movement between the damper members, the inner damper member may be mounted telescopically within the outer member along the axis of the damper. In such case, the degree to which the inner and outer damper members are axially displaced and the degree to which the apertures thereof are in registry is determinative of the amount of air flow through the damper.
In an embodiment of the invention, the damper may further include inner and outer skirt portions connected to the respective inner and outer damper members. The outer skirt portion facilitates guiding the movement of the inner skirt portion to maintain the respective inner and outer damper members in coaxial and telescoping relationship when the damper members are moved relative to one another axially along the axis of the damper.
In an embodiment of the invention, the funnel shape damper members are arranged for relative movement rotationally about the axis of the damper. In such embodiment, the degree to which the inner and outer damper members are angularly displaced and the degree to which the apertures thereof are in registry is determinative of the amount of air flow through the damper. Also, in such embodiment skirt portions may be connected to the respective inner and outer damper members. Here, the outer skirt portion guides the movement of the inner skirt portion when the damper members are moved relative to one another rotationally about the axis.
In an embodiment of the invention, the outer skirt portion is sized to closely fit into a duct such as an HVAC duct. The outer skirt portion is secured into engagement with the duct by means of, for example, a snap-in technique. More particularly, in accordance with an embodiment of the invention, the duct includes an annular bead and the outer skirt portion includes one or more nodules which snap into the bead when the outer skirt portion is inserted into the first duct. The damper and duct may together form a damper assembly which may further be installed into an existing duct having a slightly larger cross section than that of the duct in which the damper is inserted. The damper assembly may be secured to the existing duct by means of a sheet metal screw or, if the existing duct is a flexible duct, by means of friction between the two ducts.
In an embodiment of the invention, the apertures of the respective damper members are arranged in matching patterns. The shape of the apertures of the respective damper members may be any suitable shape, for example, circular. Also, the apertures of one damper member may be substantially similar in shape as the apertures of the other damper member. In an exemplary embodiment, the apertures are sized and arranged so that when the damper members are in the open position, the apertures align in a direction substantially perpendicular to the wall(s) of each damper member. Such an arrangement provide substantially unimpeded flow through the damper.
In an embodiment of the invention, the wall(s) of the respective damper members form a frustopyramidal shaped damper.
In an embodiment of the invention, the wall(s) of the respective damper members form frustoconical shaped damper members. In such embodiment, the axis of the damper is coincident with the center axes of the frustoconical shaped damper members. Such damper members may be operative to relatively move rotationally about or axially along the axis.
In an embodiment of the invention, the closed position of the damper members constitutes the apertures of one damper member being fully blocked by the imperforate portions of the other damper member. To this end, the imperforate portions may be made larger than the apertures to provide tolerance in a shut-off condition of the damper.
In an embodiment of the invention, the axis of the damper is defined by a direction of flow through the damper and the damper members are relatively movable axially along the axis. In such a damper, the degree to which the at least one walls of the respective damper members are axially displaced and the degree to which the apertures thereof are in registry is determinative of the amount of air flow through the damper. The damper may include an actuating assembly for relatively moving the damper members axially along the axis. To accomplish this, the actuating assembly may include a drive member for linearly reciprocating one damper member relative to another damper member along the axis. A motive source such as a motor may be used for moving the drive member. The motive source may be positioned proximate to the drive member or, alternatively, remote from the drive member and connected thereto by a cable-sleeve assembly.
In an embodiment of the invention, the damper includes a controller for controlling the relative movement between the damper members. The damper may also include a temperature sensor for detecting temperature of a space into which the damper conveys air and The controller may control the relative movement between the damper members based on a sensed temperature in a room and/or based on the pressure drop across the damper.